UART protocol v3 adds a slot byte to input frames (v2 still accepted as
slot 0) and slot-tagged BB 03 rumble frames. The regular firmware exposes
SWITCH_PICO_UART_CONTROLLERS (default 4) Switch Pro interfaces like the
AIO build. The bridge shares one serial port across controllers, maps
index:port[:slot], and demuxes rumble by slot.
Add per-profile native solo routing, stick/click swapping, SL/SR output mappings, and digital left-stick directions with analog priority. Extend both codecs to schema 11 while preserving legacy profiles, expose the controls and preview in Studio, and carry rail outputs through Pro emulation. Verified with 541 tests, firmware builds, editor checks, and saved-profile preservation during native 0.89 deployment.
